I've done those bench presses before we also have that same cambered bar. The bands create of ton of instability in the bench press, I would be a little apprehensive to try the same with anything heavy on squats. I do not think it would be anywhere close to an equivalent, but it certainly could make for some interesting assistance work.

I've seen someone on youtube hand a second barbell from a set of chains off the top barbell, that seems like it would be the closest to replicating a cambered bar movement. I think the video was posted here of a guy doing good mornings with that setup.

I'm inclined to agree.

Is there anyone you know that can make a couple of the T-sections (the parts that hang below the barbell, attached to it), a welder maybe, so that you just add an attachment to the barbell already available to you? Something that you can slide on and off, I mean, and therefore carry with you to the gym.